Comment 5 for bug 254840

I can confirm the problem. Adding my mouse and keyboard to the ServerLayout solved the problem.

It's a bug since, as the documentation says, InputDevice entries in the ServerLayout sections are not mandatory.

"One of these entries should be given for each input device being used in a session. Normally at least two are required, one each for the core pointer and keyboard devices. If either of those is missing, suitable InputDevice entries are searched or using the method described above in the INPUTDEVICE section. "